No matter how you cut it, till it or plow it, companion planting is growing in popularity every year. It experienced a resurgence in the 90s and is going strong.
The origins of the companion planting can be traced back to approximately 10,000 years ago. One report written by Quazi Abdul Fattah at the Department of Botany, University of Dhaka in Bangladesh on companion planning, "Plant Resources for Human Development-Nitrogen in Rice" at Dhakai.com, states that the Chinese were practicing companion planting for at least 1,000 years. According to the report, the Chinese were planting mosquito ferns (Azolla spp) as companion plants for rice crops for at least 1,000 years. The report notes, “They host a cyanobacterium that fixes nitrogen from the atmosphere, and they block light from plants that would compete with the rice.”
One of the oldest forms of companion planting in the Americas can be traced back 10,000 years, when indigenous peoples planted, “The Three Sisters.” That particular technique is believed to have originated in Mexico and was the planting of winter squash, maize (corn) and climbing beans together. Those 3 particular crops were carried northward over thousands of years, all the way up to the natives peoples in North Dakota and in New York state and Canada.
The “Three Sisters” were the primary trade goods. The process involves creating mounds with flat tops are built for each group of crops. The mounds are 12” high and 20” wide. Maize seeds were planted close together in the middle of each mound. When the maize reaches 6”, the beans and winter squash are planted around the maize, usually with 2 different types of seeds. The crops have a symbiotic relationship as the maize provides a trellis for the beans to cling to, which eliminates the need for any other support. The beans provide fixed nitrogen to the soil that the other 2 plants use. The squash spreads on the ground, blocking the sunlight, which in turn helps prevent weeds. The squash is alsoa “living mulch” that keeps the soil moist and the hairs of the vines of the plant deters pests.
One category of companion planting is the “Hedged investment.” This references the fact that “growing different crops in the same space increases the odds of some yield being given, even if one crop fails.” Some crops can provide protection from the wind, some can help deter pest insects, while others deter pathogenic fungi from damaging the crops through chemical means.
Several plants offer “predator recruitment” and “positive hosting.” In that manner, some companion plants are used because they produce nectar or pollen in the vegetable garden. This is said to encourage high populations of beneficial insects that control pests. Many predatory insects consume pests in their larval form. It also helps encourage pollination by attracting butterflies and bees.
Some of the benefits of companion planning can be keys to successful gardening in the harsh summers of west Texas. The plants that offer shade help with saving water which helps ensure plants won’t dry out. Tall plants offer natural support for climbing plants. Other plants can help block the wind, especially the warm west Texas winds that arrive every year.
Perhaps the biggest contribution comes from plants that help make nitrogen available, such as beans and peas. Plants with long taproots, like burdock, bring nutrients from deep in the soil that then enriches the topsoil, which benefits plants with shallower roots. Potatoes are an important companion crop since they minimize open areas where weeds like to grow. This can save you hours of kneeling down and working your way slowly through the rows pulling weeds and hoeing in your garden.
Some popular companion plants are:
Dill and Basil are planted alongside tomatoes to prevent hornworms. Sage spread around in a cabbage patch can help reduce injury from cabbage moths. But it also helps other crops since cabbage moths are notorious for destroying cabbage, tomatoes, Brussel sprouts, broccoli and sunflowers. Marigolds are great at deterring nematodes that attack vegetable roots, especially tomatoes. Nasturtiums attract aphids that would damage or destroy other plants. Carrots, dill, parsley and parsnips attract praying mantises, ladybugs and spiders. Those insects eat pest insects that can devastate a garden. Bush beans and corn grow well together because their roots occupy different levels of the soil and don’t compete for water. Catnip and rosemary are also effective at deterring cabbage moths. Mint will deter ants and cabbage moths. Thyme wards off cabbageworms. Lavender will deter codling moths. Zinnias attract ladybugs, which kill destructive insects. But, there are plants that do not work well together such as white garlic and onions with beans and peas. The garlic and onions will stunt the growth of the beans and peas. Potatoes and beans will not grow well if planted along with sunflowers, while cabbage and cauliflower don’t like each other too much.
Companion planting isn’t just an effective tool for the vegetable gardener, it can also be used by flower gardeners. Many times people will plant a flowerbed with a variety of colorful flowers, keep it irrigated and fertilized and wonder why it failed.
Likewise, trees can have a detrimental effect on some plants. For example the black walnut tree, whose bark, leaves, and roots contain juglone, a compound toxic to many other plants, including most vegetables. This is an example of allelopathy, where one plant secretes a substance harmful to others. But allelopathy can also be helpful to farmers; a 1998 dissertation project published online by Weed Biology and Management suggested that it might be a factor in why squash plants so successfully suppress weeds in corn fields.
Early season, cool-weather crops keep weeds at bay before later crops can be set out or mature; Vetches planted in fall protect soil from eroding and add nitrogen and organic matter to it when dug under in spring, improving both its nutrient content and its structure.
There are now a variety of websites dedicated to companion gardening and information can be found by Googling the subject. A popular book that possibly did more to bring back companion planting than any other publication is the book by Louise Riott, Carrots Love Tomatoes. The book is a bestseller, published in 1998 and it is still a favored reference used by companion plant gardeners.
Overall, companion planting can reduce weeds, improves the use of space, reduces the number and detrimental effect of a variety of garden pests and can provide protection from the elements, such as heat and wind. The increase in yield can be substantial and help with the economics of gardeners who sell their produce at farmer’s markets. It also helps in reducing the chemicals such as pesticides and herbicides that some gardeners use, which means that the produce is healthier.
Effective companion planting can reduce stress in the garden and in the gardener.